Castle Cake With Moving Parts?

I am making a castle cake for my granddaughter's b-day and I would like to have the one of my layers spin around with 2 other cakes on top of it? Has anyone done this before that could help me with this? I live in Toronto and also need to know where to buy the parts I need to make this work?Thanks for the help.Sue

Thanks I did a fire truck for my grandson with flashing lights and siren and asked for help here and no one had done it before so I figured it out on my own I guess I am on my own with this one and then I can let everyone know how to do it.

I would like the top 2 tiers to spin. But I don't know where to go here in Canada to buy the parts I need to have this work, then I need to know how to attach everything so it will work. Maybe this won't really happen if I can't find working parts? Does anyone live in the Toronto area that can help me find the parts I need? Duff does this all the time but you don't always get to see how he does everything to make it work. I wish he would show more detail on one cake rather then showing several cake with bits and pieces.Thanks